Hi folks, me again...
Our Union is concerned about the exposure that our members are
getting in a specific (narrow) frequency range.

The frequency is high in the end of audible sound, and is quite
intense.  It causes some transitory tinitus and 'headaches' in
some individuals.  Dual hearing protection is worn (Peltor-type
high noise environment plus c{*filter*}plugs of various types).  Despite
the PPE, the noise persists and wipes out all other audible sound.

Howe can this high frequency (audible range) be measured against
exposure limits?  I would expect that the more damaging frequency
range (to our cilia, etc.) would mandate a lower exposure limit.
Am I correct in any conventional way?  

We are strongly urging the employers assistance by
having them prescribe Clark-type ANC headsets and mics.
 Would this be 'worth' the expense?

Please post to these ng's as I feel that many 'out there' are
also interested in any answers.

Brotherhood of Locomotive Engineers
Safety and Health, Cab Committee
Revesltoke BC Canada